Cook Strait Giant Weta

What should a restored invertebrate fauna look like? Should we be fussed, or should we just be concerned that there is enough biomass of- whatever- to support more interesting higher animals? Is an obsession with charismatic macroinvertebrates a thing, and is it unhealthy?

Inverts have been short-changed in many ways: they are little studied, little-cared-about, sometimes actively disliked by people. It’s highly likely that many incredibly interesting insects, spiders, slaters, snails, slugs, velvet worms and centipedes have been lost for all time from New Zealand, before they were even known to science. We can’t fix that, but we can consider from within the extant taxa what invert biodiversity would be appropriate for Puangiangi.

If we can maintain the predator-free status of the island, prevent incursions of foreign insects like Argentine ants, and ensure that the native vegetation does not become any less diverse, and that its area expands, then we can protect inverts that are already there or that might be able to fly in, be blown in or float in. We are left to think about the ground-dwelling, flightless animals that might have been hardest-hit or extirpated by rats, and inverts that are known from the ecological district that could be expected to be there. So, I think that steers us towards the well known and interesting macroinvertebrates as a matter of course, rather than as a result of an obsession with making a bug zoo. Weta, Cook Strait click beetle, ngaio weevil, flax weevil, Mimopeus beetles, large snails, Peripatus, stick insects come to mind.

Puangiangi already has extremely strong numbers of tree weta; cave weta are present; ground weta might well be but given how cryptic they are, we don’t know. Cook Strait giant weta haven’t been recorded. Mimopeus beetles have recovered rapidly after rats were removed. Flax weevil were confirmed soon after we took over, and their feeding sign is everywhere. It’s interesting that they have little effect on the flax plants they feed on, given the mess the translocated population on Mana may be making. Ngaio weevil and Cook Strait click beetle we haven’t spotted yet, and they could be future targets for translocation. The divaricating shrubs are alive with mating stick insects during the late-summer nights. We have seen a peripatus and some centipedes; Powelliphanta snails are not there, and possibly never were.

As for Cook Strait giant weta, we know they are naturally present elsewhere in the ecological district- on Takapourewa, Kuru Pongi and Mana. They would also be worthy candidates for translocation as they are endemic to the region, and classified as range restricted and vulnerable. They have been translocated successfully to Maud and Matiu Somes (from Mana), Wakaterepapanui (from Takapourewa), Titi and Long Island (from Maud).

The population with the ideal combination of commonness, genetic diversity, closeness and accessibility is on Takapourewa and so, beginning in February 2014, the rangers on Takapourewa began night searches to capture suitable animals. Polly Hall and Andre de Graaf aimed for a range of ages of animals, rather than all big ones, as it is thought that they might only breed once and we did not want to move senescent animals.

Polly and Andre made a holding pen out of a mussel float and stocked it with soil, sticks and branches, topping it up with fresh taupata, tauhinu, carrot and courgette every few days. The animals were held for up to several weeks between supply boats, and batches were packaged up in modified tackle boxes and dropped off as the boat went back to Havelock past Puangiangi. Peter had selected a piece of country similar to their preferred habitat on Takapourewa, which just happened to be right by where the DOC boat could nudge on to the beach. Over three years, 300 weta (52 adult males, 110 adult females and 132 juveniles) were caught, and all but a few were taken directly to Puangiangi in ten trips finishing in September 2016. A few pairs were bred up at Eco World and Tui Nature Reserve, for the 17 progeny to be taken out to Puangiangi too.

The transfer was acknowledged by forty-odd Ngati Koata, project reps, friends, neighbours and DOC staff during a ceremony on 31 March 2017, which was also the 5th anniversary of purchase of the island. This was the easiest and cheapest project I’ve been involved in where DOC was a major participant. Polly and Andre would get in touch with us when something was happening, rather than us having to follow up, went out at night to catch the animals, looked after them and arranged to have them delivered and let go, wrote it down and reported on it, without any sweat at all being raised by me.

We have been out at night to look for them quite a few times. Numbers seen have been incredibly low, but are perhaps just starting to pick up, with one or two able to be found sheltering in the daytime also. Other translocations that have worked have also had very low encounter rates for several years and we are unconcerned, unless of course predators arrive.

A book everyone should have: Andrew Crowe, Which New Zealand Insect?, 127 pp, Penguin Books, 2002.